1. Field of the Invention
The present invention relates to an image viewing apparatus and, more particularly, to the image viewing apparatus suitably applicable to an image viewing system such as a viewfinder of a camera, a so-called head-mounted display, a goggle type display, or the like and to an image pickup device such as a camera.
2. Related Background Art
Downsizing of the whole apparatus has been demanded for image viewing apparatuses such as the head-mounted displays (HMDs), goggle type displays, etc. A variety of optical systems for meeting this demand have been suggested heretofore.
Applicant of the present application suggested in Japanese Laid-open Patent Application No. 7-333551, No. 8-50256, No. 8-160340, and No. 8-179238 the image viewing apparatus using an LCD (liquid crystal display) as display means for displaying image information and a small prism as a viewing optical system while achieving the downsizing of the whole apparatus.
The above applications describe that light emitted from the LCD displaying the image information is made incident into the small prism and then is guided via a refracting surface and a total reflection surface having curvature, formed in the small prism, and then via a reflecting surface out of the small prism toward a viewer. This causes an enlarged virtual image of the image information displayed on the display means (LCD) to be formed ahead of the viewer, whereby the viewer can view the virtual image.
In an image viewing apparatus such as an HMD etc., it is a significant challenge to decrease the overall size and weight of apparatus, because the apparatus is mounted on the head part of viewer. Another important challenge is to broaden the viewing angle in order to provide the viewing of the image information displayed on the display means with strong appeal.